Power amplifier circuit

ABSTRACT

Provided is a power amplifier circuit that can increase output power and also reduce the effect of intermodulation distortion. The power amplifier circuit includes a power divider, a distortion compensation circuit provided on the secondary path, a power combiner, and a first amplifier configured. The distortion compensation circuit includes a generation circuit configured to generate the second-harmonic wave of the input signal, a filter circuit configured to attenuate the fundamental wave and pass the second-harmonic wave, and a phase adjustment circuit configured to adjust the phase of the second-harmonic wave.

This is a continuation of International Application No.PCT/JP2019/001687 filed on Jan. 21, 2019 which claims priority fromJapanese Patent Application No. 2018-008659 filed on Jan. 23, 2018. Thecontents of these applications are incorporated herein by reference intheir entireties.

BACKGROUND Technical Field

The present disclosure relates to a power amplifier circuit.

Mobile communication devices, such as mobile phones include poweramplifiers for amplifying electric power of transmit signals. In thecase in which, for example, a plurality of signals with adjacentfrequencies are inputted to the power amplifier, these signals may causeintermodulation distortion (IMD) and gain linearity may become worse. Inthis regard, with the aim of reducing the effect of such intermodulationdistortion, a technology of deliberately adding a harmonic wave in asignal path to cancel out intermodulation distortion components has beendeveloped. For example, Patent Document 1 discloses a distortioncompensating and power amplifying apparatus in which the output of anamplifier of a first stage is split into a fundamental wave and asecond-harmonic wave, the second-harmonic wave is changed in phase andamplitude, the second-harmonic wave is then combined with thefundamental wave, and the resultant wave is inputted to anotheramplifier of a subsequent stage, so that compensation forintermodulation distortion is achieved.

Patent Document 1: U.S. Patent Application Publication No. 2005/0242877

BRIEF SUMMARY

In recent years, due to the introduction of new communication standards,such as the fourth-generation (4G) mobile communication system and thefifth-generation (5G) mobile communication system, the number offrequency bands that power amplifier circuits need to support hasincreased, and thus, the number of filter circuits has also increased.Since this increases insertion loss at the front-end, for the purpose ofcompensating for the loss, demand for increased output power of transmitsignals transmitted by mobile phones has risen. Thus, as describedabove, in the case in which a harmonic wave is deliberately added forthe purpose of compensating for intermodulation distortion, as outputpower of transmit signals are increased, power of the added harmonicwave needs to be increased. However, since in the apparatus disclosed inPatent Document 1 the second-harmonic wave occurring at the amplifier ofthe first stage is added, power of the second-harmonic wave may beinsufficient for power of transmit signals.

The present disclosure provides a power amplifier circuit that canincrease output power and also reduce the effect of intermodulationdistortion.

A power amplifier circuit according to an aspect of the presentdisclosure includes a power divider configured to divide an input signaland output the divided input signal to a primary path and a secondarypath, a distortion compensation circuit provided on the secondary path,a power combiner configured to combine a fundamental wave of the inputsignal having traveled along the primary path with a second-harmonicwave of the input signal having traveled along the secondary path, and afirst amplifier configured to amplify a combined signal outputted fromthe power combiner and output an amplified signal. The distortioncompensation circuit includes a generation circuit configured togenerate the second-harmonic wave of the input signal, a filter circuitconfigured to attenuate the fundamental wave and pass thesecond-harmonic wave, and a phase adjustment circuit configured toadjust the phase of the second-harmonic wave.

The present disclosure can provide a power amplifier circuit that canincrease output power and also reduce the effect of intermodulationdistortion.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram illustrating a configuration example of a poweramplifier circuit according to a first embodiment of the presentdisclosure.

FIG. 2 is a diagram illustrating the spectrum of a signal inputted to anamplifier 111 of a posterior stage.

FIG. 3 is a diagram illustrating part of the spectrum of a signaloutputted from the amplifier 111 of the posterior stage.

FIG. 4A is a graph indicating simulation results of third-orderintermodulation distortion in the power amplifier circuit according tothe first embodiment of the present disclosure and a comparativeexample.

FIG. 4B is a graph indicating simulation results of third-orderintermodulation distortion in the power amplifier circuit according tothe first embodiment of the present disclosure and the comparativeexample.

FIG. 5 is a graph indicating a simulation result of the gaincharacteristic of the power amplifier circuit according to the firstembodiment of the present disclosure and the comparative example.

FIG. 6 is a diagram illustrating a configuration example of a poweramplifier circuit according to a second embodiment of the presentdisclosure.

FIG. 7 is a diagram illustrating a configuration example of a transmitmodule including the power amplifier circuit according to the firstembodiment of the present disclosure.

FIG. 8 is a diagram illustrating another configuration example of atransmit module including the power amplifier circuit according to thefirst embodiment of the present disclosure.

FIG. 9 is a diagram illustrating a configuration example of a transmitmodule including the power amplifier circuit according to the secondembodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure are described indetail with reference to the drawings. It should be noted that the sameelements are assigned the same reference characters and redundantdescriptions are omitted.

FIG. 1 is a diagram illustrating a configuration example of a poweramplifier circuit according to a first embodiment of the presentdisclosure. A power amplifier circuit 100A illustrated in FIG. 1 isprovided in, for example, a mobile communication device, such as amobile phone and used for amplifying electric power of radio frequency(RF) signals to be transmitted to base stations. The power amplifiercircuit 100A amplifies power of signals of communication standards, suchas the second-generation (2G) mobile communication system, thethird-generation (3G) mobile communication system, the 4G mobilecommunication, the 5G mobile communication system, Long-Term EvolutionFrequency-Division Duplex (LTE-FDD), Long-Term Evolution Time-DivisionDuplex (LTE-TDD), LTE-Advanced, and LTE-Advanced Pro. The frequency ofRF signals ranges, for example, from about several hundreds of MHz toabout several tens of GHz. The communication standard and the frequencyof signals amplified by the power amplifier circuit 100A are not limitedto these examples.

The power amplifier circuit 100A includes, for example, amplifiers 110and 111, a power divider 120, a power combiner 130, matching circuits140 and 141, a harmonic termination circuit 150, a distortioncompensation circuit 160, an input terminal T1, and an output terminalT2. The power amplifier circuit 100A also includes a primary path P1 anda secondary path P2.

The amplifier 110 (a third amplifier) and the amplifier 111 (a firstamplifier) both amplify inputted RF signals and output the RF signals.This means that the power amplifier circuit 100A amplifies electricpower in two stages. Specifically, the amplifier 110 of a first stage (adrive stage) amplifies an RF signal RF1 inputted from the input terminalT1 via the matching circuit 140 and outputs an RF signal RF2 (an inputsignal). The amplifier 111 of a posterior stage (a power stage)amplifies an RF signal RF3 (a combined signal) resulting fromcombination by the power combiner 130 described later and outputs an RFsignal RF4. The RF signals RF2 and RF4, each includes a harmonic waveincluding the second-harmonic wave generated by amplification of theamplifier 110 or 111. The amplifiers 110 and 111 are both configured byusing bipolar transistors, such as heterojunction bipolar transistors(HBTs). The amplifiers 110 and 111 may be configured by using fieldeffect transistors (MOSFETs: Metal-oxide-semiconductor Field-EffectTransistors) instead of HBTs.

The power divider 120 divides the RF signal RF2 (the input signal)outputted by the amplifier 110 of the first stage and outputs thedivided RF signal RF2 to the primary path P1 and the secondary path P2.The primary path P1 is a path starting from the input terminal T1 andleading to the output terminal T2 via the matching circuit 141. Theprimary path P1 is a path along which a fundamental wave F₀ of the RFsignal RF1 travels. The secondary path P2 is a path starting from thepower divider 120 and leading to the power combiner 130 via thedistortion compensation circuit 160. The secondary path P2 is a path forgenerating a second-harmonic wave 2F₀ to compensate for third-orderintermodulation distortion caused at the amplifier 111 of the posteriorstage. The power divider 120 is not limited to an element, such as acoupler but only need to be configured to divide RF signals. Forexample, the power divider 120 may be a branch point at which the signalpath is separated into the primary path P1 and the secondary path P2.

The power combiner 130 generates the RF signal RF3 (the combined signal)by combining the fundamental wave F₀ having traveled along the primarypath P1 and the second-harmonic wave 2F₀ having traveled along thesecondary path P2 with each other. The generated RF signal RF3 isoutputted to the amplifier 111 of the posterior stage.

The matching circuit 140 (MN: Matching Network) performs impedancematching between a circuit (not illustrated in the drawing) provided inan anterior stage and the amplifier 110.

The matching circuit 141 is provided between the power divider 120 andthe power combiner 130 on the primary path P1 and performs impedancematching between the amplifiers 110 and 111. The matching circuit 141also has a function of attenuating harmonic distortion (HD) caused byamplification of the amplifier 110. This means that the matching circuit141 is configured as a specific example of a second-harmonic-waveattenuation circuit. This configuration hinders output of thesecond-harmonic wave to the power combiner 130 through the primary pathP1. Specifically, the matching circuit 141 may be, for example, alow-pass-filter (LPF) circuit having a frequency characteristic ofpassing the fundamental wave and attenuating the second-harmonic wave.

The harmonic termination circuit 150 is provided in a subsequent stageafter the amplifier 111. The harmonic termination circuit 150 grounds,for example, the second-harmonic wave included in the RF signal RF4. Asa result, the output terminal T2 outputs a transmit signal in which thesecond-harmonic wave has been attenuated. The harmonic terminationcircuit 150 may have a function of impedance matching between theamplifier 111 and a circuit in a posterior stage after the outputterminal T2.

The distortion compensation circuit 160 is provided between the powerdivider 120 and the power combiner 130 on the secondary path P2. Thedistortion compensation circuit 160 is a circuit configured to generatethe second-harmonic wave 2F₀, which is deliberately added to compensatefor third-order intermodulation distortion, and amplifies and outputsthe second-harmonic wave 2F₀. Specifically, the distortion compensationcircuit 160 includes, for example, a harmonic-wave generation circuit200, a filter circuit 210, an amplifier 220, a phase adjustment circuit230, and a matching circuit 240.

The harmonic-wave generation circuit 200 generates the second-harmonicwave 2F₀ of the RF signal RF2 from the RF signal RF2 outputted to thesecondary path P2 by the power divider 120. The harmonic-wave generationcircuit 200 may be formed as, for example, an amplifier that amplifiesthe RF signal RF2. Alternatively, the harmonic-wave generation circuit200 may be formed as a multiplier circuit that doubles the frequency ofthe fundamental wave F₀ inputted from the power divider 120 to thesecondary path P2.

The filter circuit 210 is provided in, for example, a subsequent stageafter the harmonic-wave generation circuit 200. The filter circuit 210has a frequency characteristic of attenuating the fundamental wave F₀and passing the second-harmonic wave 2F₀. With this configuration, inthe case in which the harmonic-wave generation circuit 200 of theanterior stage is formed as, for example, the amplifier, only thesecond-harmonic wave 2F₀, which is to be used for compensation fordistortion, is extracted from the signal outputted from the amplifier.The filter circuit 210 may be configured as, for example, ahigh-pass-filter (HPF) circuit or a band-pass-filter (BPF) circuit thatattenuates the fundamental wave F₀ and passes the second-harmonic wave2F₀.

The amplifier 220 (a second amplifier) is provided in, for example, asubsequent stage after the filter circuit 210. The amplifier 220amplifies the amplitude of the second-harmonic wave 2F₀ inputted via thefilter circuit 210 and outputs the second-harmonic wave 2F₀ to the phaseadjustment circuit 230. Since the distortion compensation circuit 160includes the amplifier 220, when the level of output power of thetransmit signal is relatively high, the power of the second-harmonicwave 2F₀ can be also increased in accordance with the level. In the casein which the output level of the harmonic-wave generation circuit 200satisfies a level required for the second-harmonic wave 2F₀, theamplifier 220 is not necessarily included in the distortion compensationcircuit 160.

The phase adjustment circuit 230 is provided in, for example, asubsequent stage after the amplifier 220. The phase adjustment circuit230 performs adjustment to render the phase of the generatedsecond-harmonic wave 2F₀ suitable for distortion compensation andoutputs the second-harmonic wave 2F₀.

The matching circuit 240 performs impedance matching between the phaseadjustment circuit 230 and the amplifier 111.

With the configuration described above, the distortion compensationcircuit 160 can generate the second-harmonic wave 2F₀ that is to bedeliberately added to the input of the amplifier 111. The order in whichthe components included in the distortion compensation circuit 160 arearranged is not limited to this example and may be changed asappropriate. For example, the amplifier 220 may be provided in asubsequent stage after the phase adjustment circuit 230. Furthermore,the power divider 120, the power combiner 130, the matching circuits140, 141, and 240, the harmonic termination circuit 150, the filtercircuit 210, and the phase adjustment circuit 230 may be each configuredto include elements, such as an inductor and a capacitor, or a resonatorusing acoustic waves, such as a surface-acoustic-wave (SAW) filter.

Next, with reference to FIGS. 2 and 3, effects of compensation forthird-order intermodulation distortion are described. FIG. 2 is adiagram illustrating the spectrum of a signal, which is the RF signalRF3 in FIG. 1, inputted to the amplifier 111 of the posterior stage.FIG. 3 is a diagram illustrating part of the spectrum of a signal, whichis the RF signal RF4 in FIG. 1, outputted from the amplifier 111 of theposterior stage. In graphs illustrated in FIGS. 2 and 3, the horizontalaxes indicate the frequency of the signal and the vertical axes indicatethe power spectral density (PSD).

As indicated in FIG. 2, the fundamental wave F₀ having traveled alongthe primary path P1 and the second-harmonic wave 2F₀ having traveledalong the secondary path P2 are inputted to the amplifier 111 of theposterior stage. Here, the fundamental wave F₀ contains components oftwo kinds of frequencies f₁ and f₂ (f₁<f₂) adjacent to each other. Inthis case, the second-harmonic wave of each of the two kinds offrequencies f₁ and f₂ is generated in the secondary path P2, and thus,the second-harmonic wave 2F₀ contains components of two kinds offrequencies 2 f ₁ and 2 f ₂. As such, signals at the frequencies f₁ andf₂ and signals at the frequencies 2 f ₁ and 2 f ₂ are inputted togetherto the amplifier 111.

Subsequently, as the effect of amplification of the amplifier 111, anamplified signal obtained by amplifying the fundamental wave F₀ isoutputted as indicated in FIG. 3. Additionally, as the effect ofamplification of the amplifier 111, third-order intermodulationdistortion IM3_(L) with a frequency 2 f ₁-f₂ occurs on a low-frequencyside with respect to the fundamental wave F₀ while third-orderintermodulation distortion IM3_(H) with a frequency 2 f ₂-f₁ occurs on ahigh-frequency side with respect to the fundamental wave F₀. Thethird-order intermodulation distortions IM3_(L) and IM3_(H) arerelatively close to the frequencies f₁ and f₂ of the fundamental waveF₀, and hence, it is difficult to remove the third-order intermodulationdistortions IM3_(L) and IM3_(H) by using a filter circuit or the like.The third-order intermodulation distortions IM3_(L) and IM3_(H) can be,therefore, a cause of deterioration of linearity of the amplifier. Theamplification of the amplifier 111 also causes, for example, other kindsof distortion, such as third-order intermodulation distortions withfrequencies 2 f ₁+f₂ and 2 f ₂+f₁, but the frequencies of thedistortions are relatively far from the frequencies f₁ and f₂ of thefundamental wave F₀ and descriptions thereof is thus omitted here.

For the purpose of compensating for the third-order intermodulationdistortions IM3_(L) and IM3_(H), which is relatively close to thefundamental wave F₀, compensation signals CS_(L) and CS_(H) that cancelout the third-order intermodulation distortions IM3_(L) and IM3_(H) aregenerated by deliberately adding the second-harmonic wave 2F₀ in thisembodiment. Specifically, a signal obtained by adding the fundamentalwave F₀ and the second-harmonic wave 2F₀ in the power combiner 130 isinputted to the amplifier 111, and as a result, the compensation signalCS_(L) with a frequency (2 f ₁-f₂), which is a difference between thefrequency 2 f ₁ as one frequency of the second-harmonic wave 2F₀ and thefrequency f₂ as the other frequency of the fundamental wave F₀, isgenerated. Additionally, a compensation signal CS_(H) with a frequency(2 f ₂-f₁), which is a difference between the frequency 2 f ₂ as theother frequency of the second-harmonic wave 2F₀ and the frequency f₁ asone frequency of the fundamental wave F₀, is generated. Thesecompensation signals CS_(L) and CS_(H) are respectively identical infrequency to the third-order intermodulation distortions IM3 _(L) andIM3 _(H). Furthermore, the phase adjustment circuit 230 changes thephase of the second-harmonic wave 2F₀ in such a manner that thecompensation signals CS_(L) and CS_(H) are almost opposite in phase tothe third-order intermodulation distortions IM3 _(L) and IM3 _(H) at theoutput of the amplifier 111. Moreover, the amplifier 220 amplifies theamplitude of the second-harmonic wave 2F₀ in such a manner that thecompensation signals CS_(L) and CS_(H) and the third-orderintermodulation distortions IM3 _(L) and IM3 _(H) cancel each other outat the output of the amplifier 111 with respect to amplitude. As such,as illustrated in FIG. 3, the compensation signals CS_(L) and CS_(H)cancel out the third-order intermodulation distortions IM3 _(L) and IM3_(H). In FIG. 3, the compensation signals CS_(L) and CS_(H) are drawn ina downward direction to indicate that the compensation signals CS_(L)and CS_(H) are almost opposite in phase to the third-orderintermodulation distortions IM3 _(L) and IM3 _(H).

Due to the effect described above, in the power amplifier circuit 100A,it is possible to reduce the effect of the third-order intermodulationdistortions IM3 _(L) and IM3 _(H) occurring in the amplifier 111. As aresult, the power amplifier circuit 100A can hinder the deterioration oflinearity.

The configuration disclosed in Patent Document 1 does not include acircuit between a power divider and a power combiner on a primary pathto attenuate the second-harmonic wave, and thus, the second-harmonicwave caused by amplification of the amplifier in the first stage passesthrough the primary path. As a result, in the case in which thesecond-harmonic wave is generated in a secondary path, thesecond-harmonic wave having traveled through the primary path and thesecond-harmonic wave having traveled through the secondary path maycancel each other out when the two kinds of second-harmonic waves areadded together at the power combiner. Consequently, the power of thesecond-harmonic wave additionally inputted to the amplifier 111 may beinsufficient. In this regard, in the present embodiment, the function ofattenuating the second-harmonic wave is imparted to the matching circuit141 provided in the primary path P1. With this configuration, in thepresent embodiment, a high-power second-harmonic wave can be inputted tothe amplifier 111 in comparison to the configuration disclosed in PatentDocument 1. Therefore, the power amplifier circuit 100A can increaseoutput power and also reduce the effect of intermodulation distortion.

Furthermore, in the present embodiment, the distortion compensationcircuit 160 includes the harmonic-wave generation circuit 200 forgenerating the second-harmonic wave. In the case in which theharmonic-wave generation circuit 200 is configured as an amplifier, theamplifier can be designed especially for generation of thesecond-harmonic wave. Thus, in comparison to the configuration disclosedin Patent Document 1 in which the amplifier of the first stage amplifiesthe fundamental wave and also generates the second-harmonic wave, it ispossible to generate a high-power second-harmonic wave. Moreover, in thepresent embodiment, the distortion compensation circuit 160 includes theamplifier 220 that further amplifies the amplitude of the generatedsecond-harmonic wave. Also with this configuration, the power amplifiercircuit 100A can generate a high-power second-harmonic wave incomparison to the configuration disclosed in Patent Document 1, and as aresult, it is possible to increase output power and also reduce theeffect of intermodulation distortion.

All the components included in the power amplifier circuit 100Aillustrated in FIG. 1 are not necessarily provided as individualcircuits and one circuit may have a plurality of functions. For example,it is possible that the distortion compensation circuit 160 does notinclude the filter circuit 210, but instead, the phase adjustmentcircuit 230 has a function of the filter circuit 210.

While in the embodiment described above the case in which the distortioncompensation circuit 160 generates the second-harmonic wave tocompensation for third-order intermodulation distortion is described asan example, it is possible to compensate for higher-orderintermodulation distortion. Usually, when the amplifier 111 amplifies asignal with the frequencies f₁ and f₂, (2N+1)-order intermodulationdistortion with frequencies {(N+1)f₁−Nf₂} and {(N+1)f₂−Nf₁} (N is aninteger equal to or greater than 1) is generated. As such, thedistortion compensation circuit 160 can generate harmonic waves atinteger multiples of a fundamental frequency, so that it is possible tocancel out intermodulation distortion of these high orders.

FIGS. 4A and 4B are graphs indicating simulation results of third-orderintermodulation distortion in the power amplifier circuit according tothe first embodiment of the present disclosure and a comparativeexample. Here, the comparative example has a configuration formed byexcluding the distortion compensation circuit 160 from the poweramplifier circuit 100A illustrated in FIG. 1. FIG. 4A illustratesthird-order intermodulation distortion on a low-frequency side withrespect to the fundamental wave and FIG. 4B illustrates third-orderintermodulation distortion on a high-frequency side with respect to thefundamental wave. In the graphs presented in FIGS. 4A and 4B, thehorizontal axes indicate the output power Pout (dBm) of transmit signaland the vertical axes indicate the output level (dBc) of third-orderintermodulation distortion with respect to the fundamental wave.

As illustrated in FIGS. 4A and 4B, both in the present embodiment andthe comparative example, the output level of third-order intermodulationdistortion steeply rises after the output level exceeds a particularoutput power level. However, for example, in the case of comparison ofoutput power when distortion is −35 dBc, referring to FIG. 4A, theoutput power of the comparative example is approximately 31 dBm whilethe output power of the present embodiment is approximately 32.5 dBm,which indicates that the output power of the present embodiment isimproved by approximately 1.5 dB as compared to the comparative example.Furthermore, referring to FIG. 4B, the output power of the comparativeexample is approximately 30.5 dBm while the output power of the presentembodiment is approximately 32.5 dBm, which indicates that the outputpower of the present embodiment is improved by approximately 2.0 dB ascompared to the comparative example. According to these results, it isunderstood that the present embodiment increases output power and alsoreduces the effect of intermodulation distortion.

FIG. 5 is a graph indicating a simulation result of the gaincharacteristic of the power amplifier circuit according to the firstembodiment of the present disclosure and the comparative example. In thegraph presented in FIG. 5, the horizontal axis indicates the outputpower Pout (dBm) of transmit signal and the vertical axis indicates gain(dB).

As illustrated in FIG. 5, in comparison to the comparative example,although overall gain in the present embodiment slightly falls, therange in which gain remains at a certain level while the output powerPout increases is extended. Accordingly, the present embodiment isimproved with respect to linearity as compared to the comparativeexample. Moreover, gain in the comparative example sharply falls afterthe output power exceeds approximately 30 dBm, whereas gain in thepresent embodiment only gradually falls after the output power exceedsapproximately 30 dBm. This indicates that deterioration of linearity ishindered by reducing the effect of intermodulation distortion aspresented in FIGS. 4A and 4B.

FIG. 6 is a diagram illustrating a configuration example of a poweramplifier circuit according to a second embodiment of the presentdisclosure. In the present embodiment, descriptions about specificscommon to those of the first embodiment are not repeated and onlydifferent points are explained. In particular, almost identical effectsand advantages achieved by almost identical configurations are notmentioned in every embodiment.

A power amplifier circuit 100B illustrated in FIG. 6 includes anamplifier 300 and matching circuits 310 and 311 instead of the matchingcircuit 141 as compared to the power amplifier circuit 100A illustratedin FIG. 1.

The amplifier 300 (a fourth amplifier) is provided between the powerdivider 120 and the power combiner 130 on the primary path P1 andconfigured to amplify and output the RF signal RF2 (the input signal)having been divided by the power divider 120. The amplifier 300 isdesigned to amplify the frequency range of the fundamental wave F₀. Thisenables attenuation of harmonic waves including the second-harmonic wavecaused by amplification of the amplifier 110 of the first stage. Thismeans that the amplifier 300 is configured as a specific example of asecond-harmonic-wave attenuation circuit.

The matching circuits 310 and 311 perform impedance matchingrespectively for the amplifier of the anterior stage and the amplifierof the posterior stage.

As such, attenuation of the second-harmonic wave in the primary path P1in the present embodiment can be achieved by the amplifier 300 insteadof the matching circuit 141 illustrated in FIG. 1. Also with thisconfiguration, similarly to the power amplifier circuit 100A, the poweramplifier circuit 100B can increase output power and also reduce theeffect of intermodulation distortion. Furthermore, since the poweramplifier circuit 100B includes the amplifiers 110, 300, and 111 inthree stages, it is possible to further increase output power oftransmit signal in comparison to the power amplifier circuit 100A.

FIG. 7 is a diagram illustrating a configuration example of a transmitmodule including the power amplifier circuit according to the firstembodiment of the present disclosure.

As illustrated in the drawing, a transmit module 300A includes asemiconductor chip 20A, a matching circuit 142, and bias networks 180 to183, which are provided at a module substrate 10A. At the semiconductorchip 20A, the power amplifier circuit 100A according to the firstembodiment and bias circuits 170 to 173 are provided in an integratedmanner.

The matching circuit 142 performs impedance matching between the poweramplifier circuit 100A provided in an anterior stage and another circuit(not illustrated in the drawing) provided in a posterior stage after thepower amplifier circuit 100A. The matching circuit 142 may be formedinside the semiconductor chip 20A.

The bias networks 180 to 183 supply a power supply voltage respectivelyto the amplifiers 110 and 111, the harmonic-wave generation circuit 200,and the amplifier 220. A battery voltage Vbatt is supplied to the biascircuits 170 to 173 and the bias circuits 170 to 173 in turn supply abias current or a bias voltage respectively to the amplifiers 110 and111, the harmonic-wave generation circuit 200, and the amplifier 220 inaccordance with control signals Ctrl1 to Ctrl4 inputted from outside ofthe module substrate 10A.

As described above, since the power amplifier circuit 100A including thedistortion compensation circuit 160 and the bias circuits 170 to 173 areprovided at the same semiconductor chip 20A in an integrated manner, itis possible to downsize the transmit module in comparison to, forexample, a configuration in which the distortion compensation circuit160 is formed outside the semiconductor chip 20A.

FIG. 8 is a diagram illustrating another configuration example of atransmit module including the power amplifier circuit according to thefirst embodiment of the present disclosure.

As illustrated in the drawing, the transmit module 300B differs from thetransmit module 300A in that the filter circuit 210 included in thedistortion compensation circuit 160 is formed outside a semiconductorchip 20B. This means that, in this configuration example, a harmonicwave outputted from the harmonic-wave generation circuit 200 once movesout of the semiconductor chip 20B and returns again to the semiconductorchip 20B through the filter circuit 210.

With this configuration, in the case in which the filter circuit 210 isconfigured as, for example, a SAW filter, it is possible to reduce thecost in comparison to a configuration in which the filter circuit 210 isformed at the semiconductor chip 20B. In this case, the filter circuit210 may be provided at, for example, a module substrate 10B by using asurface mount device (SMD).

FIG. 9 is a diagram illustrating a configuration example of a transmitmodule including the power amplifier circuit according to the secondembodiment of the present disclosure.

As illustrated in the drawing, a transmit module 300C differs from thetransmit module 300A in that the semiconductor chip 20A is replaced withthe semiconductor chip 20C and a bias network 184 is also included.

The semiconductor chip 20C includes the power amplifier circuit 100Baccording to the second embodiment and bias circuits 170 to 174. Thebattery voltage Vbatt is supplied to the bias circuit 174 and the biascircuit 174 in turn supplies a bias current or a bias voltage to theamplifier 300 in accordance with a control signal Ctrl5 inputted fromoutside of a module substrate 10C. The bias network 184 supplies a powersupply voltage to the amplifier 300.

Also in this case, since the power amplifier circuit 100B including thedistortion compensation circuit 160 and the bias circuits 170 to 174 areprovided at the same semiconductor chip 20C in an integrated manner, itis possible to downsize the transmit module. Also in the transmit module300C, similarly to the transmit module 300B, the filter circuit 210 maybe formed outside the semiconductor chip 20C.

The transmit modules 300A to 300C described above may each constitute ahigh-frequency module in conjunction with a receive module including alow-noise amplifier (LNA). Furthermore, a plurality of any kind of thetransmit modules 300A to 300C may constitute a multiband high-frequencymodule in conjunction with a plurality of receive modules. In this case,the plurality of modules respond respectively to signals at differentfrequency bands. The multiband high-frequency module may include modulesrespectively supporting a frequency division duplex (FDD) technique anda time division duplex (TDD) technique.

The exemplary embodiments of the present disclosure have been describedabove. The power amplifier circuits 100A and 100B include the powerdivider 120 configured to divide the RF signal RF2 and output thedivided RF signal RF2 to the primary path P1 and the secondary path P2,the distortion compensation circuit 160 provided on the secondary pathP2, the power combiner 130 configured to combine the fundamental wave F₀of the RF signal RF2 having traveled along the primary path P1 with thesecond-harmonic wave 2F₀ of the RF signal RF2 having traveled along thesecondary path P2, and the amplifier 111 configured to amplify the RFsignal RF3 outputted from the power combiner 130 and output the RFsignal RF4. The distortion compensation circuit 160 includes theharmonic-wave generation circuit 200 configured to generate thesecond-harmonic wave 2F₀ of the RF signal RF2, the filter circuit 210configured to attenuate the fundamental wave F₀ and pass thesecond-harmonic wave 2F₀, and the phase adjustment circuit 230configured to adjust the phase of the second-harmonic wave 2F₀. Withthis configuration, in comparison to the configuration in which theamplifier of the first stage amplifies the fundamental wave and alsogenerates the second-harmonic wave, the power amplifier circuits 100Aand 100B can generate a high-power second-harmonic wave. Therefore, itis possible to increase output power and also reduce the effect ofintermodulation distortion.

Furthermore, the distortion compensation circuit 160 further includesthe amplifier 220 configured to amplify the amplitude of thesecond-harmonic wave 2F₀. The amplifier 220 is positioned between theharmonic-wave generation circuit 200 and the phase adjustment circuit230. With this configuration, in comparison to the configuration withoutnecessarily the amplifier 220 that amplifies the second-harmonic wave,the power amplifier circuits 100A and 100B can generate a higher-powersecond-harmonic wave. Therefore, it is possible to increase output powerand also reduce the effect of intermodulation distortion.

Moreover, the amplifier 220 amplifies the amplitude of thesecond-harmonic wave 2F₀ in such a manner that the signals obtained asthe differences between the second-harmonic wave 2F₀ and the fundamentalwave F₀ and the third-order intermodulation distortions IM3 _(L) and IM3_(H) occurring in the amplifier 111 cancel each other out at the outputof the amplifier 111. With this configuration, when the level of outputpower of the transmit signal is relatively high, the power of thesecond-harmonic wave 2F₀ can be also increased in accordance with thelevel.

Further, the phase adjustment circuit 230 changes the phase of thesecond-harmonic wave 2F₀ in such a manner that the signals obtained asthe differences between the second-harmonic wave 2F₀ and the fundamentalwave F₀ and the third-order intermodulation distortions IM3 _(L) and IM3_(H) occurring in the amplifier 111 are substantially in antiphase atthe output of the amplifier 111. With this configuration, thecompensation signals CS_(L) and CS_(H) cancel out the third-orderintermodulation distortions IM3 _(L) and IM3 _(H), and as a result, itis possible to reduce the effect of intermodulation distortion.

Furthermore, the power amplifier circuit 100A further includes theamplifier 110 provided in the stage before the power divider 120 andconfigured to output the RF signal RF2 and the matching circuit 141provided between the power divider 120 and the power combiner 130 on theprimary path P1 and configured to attenuate a signal in the frequencyrange of the second-harmonic wave 2F₀. This configuration avoids thesecond-harmonic wave having traveled along the primary path P1 and thesecond-harmonic wave having traveled along the secondary path P2cancelling each other out at the power combiner 130. As a result, in thepower amplifier circuit 100A, a high-power second-harmonic wave can beinputted to the amplifier 111 in comparison to the configurationdisclosed in Patent Document 1.

Moreover, the power amplifier circuit 100B further includes theamplifier 110 provided in a stage before the power divider 120 andconfigured to output the RF signal RF2 and the amplifier 300 configuredto amplify the RF signal RF2 outputted to the primary path P1 by thepower divider 120. This configuration avoids the second-harmonic wavehaving traveled along the primary path P1 and the second-harmonic wavehaving traveled along the secondary path P2 cancelling each other out atthe power combiner 130. As a result, in the power amplifier circuit100B, a high-power second-harmonic wave can be inputted to the amplifier111 in comparison to the configuration disclosed in Patent Document 1.Additionally, since the power amplifier circuit 100B includes theamplifiers 110, 300, and 111 in three stages, it is possible to furtherincrease output power of transmit signal in comparison to the poweramplifier circuit 100A.

Further, in the transmit module 300B, the filter circuit 210 is formedoutside the semiconductor chip 20B at which the amplifier 111 is formed.In the case in which the filter circuit 210 is configured as, forexample, a SAW filter, it is possible to reduce the cost in comparisonto a configuration in which the filter circuit 210 is formed at thesemiconductor chip 20B.

The embodiments described above have been made for ease of understandingthe present disclosure and should not be construed to limit the presentdisclosure. The present disclosure can be changed or improved withoutnecessarily departing from its spirit and also includes equivalentsthereof. This means that modifications to the embodiments designed bythose skilled in the art as appropriate are also embodied in the scopeof the present disclosure when the modifications have features of thepresent disclosure. For example, the elements included in theembodiments, the arrangements thereof, materials, conditions, shapes,sizes are not limited to the examples and may be changed as appropriate.Furthermore, the elements included in the embodiments can be combinedwith each other when technically possible and combinations thereof maybe encompassed in the scope of the present disclosure when thecombinations have features of the present disclosure.

REFERENCE SIGNS LIST

10A-10C . . . module substrate, 20A-20C . . . semiconductor chip, 100A,100B . . . power amplifier circuit, 110, 111, 220, 300 . . . amplifier,120 . . . power divider, 130 . . . power combiner, 140, 141, 142, 240,310, 311 . . . matching circuit, 150 . . . harmonic termination circuit,160 . .. distortion compensation circuit, 170-174 . . . bias circuit,180-183 . . . bias network, 200 . . . harmonic-wave generation circuit,210 . . filter circuit, 230 . phase adjustment circuit, 300A-300C . . .transmit module, T1 . . . input terminal, T2 . . . output terminal, P1 .. . primary path, P2 . . . secondary path

The invention claimed is:
 1. A power amplifier circuit comprising: apower divider configured to divide an input signal, and to output thedivided input signal to a primary path and a secondary path; adistortion compensation circuit in the secondary path; a power combinerconfigured to combine a fundamental wave of the input signal from theprimary path with a second-harmonic wave of the input signal from thesecondary path; and a first amplifier configured to amplify a combinedsignal outputted from the power combiner, and to output an amplifiedsignal, wherein the distortion compensation circuit comprises: ageneration circuit configured to generate the second-harmonic wave ofthe input signal, a filter circuit configured to attenuate thefundamental wave and to pass the second-harmonic wave, and a phaseadjustment circuit configured to adjust a phase of the second-harmonicwave, wherein the distortion compensation circuit further comprises asecond amplifier configured to amplify an amplitude of thesecond-harmonic wave, and wherein the second amplifier is between thegeneration circuit and the phase adjustment circuit.
 2. The poweramplifier circuit according to claim 1, wherein the second amplifier isconfigured to amplify the amplitude of the second-harmonic wave suchthat a signal obtained as a difference between the second-harmonic waveand the fundamental wave cancels, at an output of the first amplifier, athird-order intermodulation distortion occurring in the first amplifier.3. The power amplifier circuit according to claim 1, wherein the phaseadjustment circuit is configured to change the phase of thesecond-harmonic wave such that a signal obtained as a difference betweenthe second-harmonic wave and the fundamental wave is substantiallyantiphase with, at an output of the first amplifier, a third-orderintermodulation distortion occurring in the first amplifier.
 4. Thepower amplifier circuit according to claim 2, wherein the phaseadjustment circuit is configured to change the phase of thesecond-harmonic wave such that the signal obtained as the differencebetween the second-harmonic wave and the fundamental wave issubstantially antiphase with, at the output of the first amplifier, thethird-order intermodulation distortion occurring in the first amplifier.5. The power amplifier circuit according to claim 1, further comprising:a third amplifier in a stage preceding the power divider, the thirdamplifier being configured to output the input signal; and asecond-harmonic-wave attenuation circuit between the power divider andthe power combiner in the primary path, the second harmonic-waveattenuation circuit being configured to attenuate a signal in afrequency range of the second-harmonic wave.
 6. The power amplifiercircuit according to claim 3, further comprising: a third amplifier in astage preceding the power divider, the third amplifier being configuredto output the input signal; and a second-harmonic-wave attenuationcircuit between the power divider and the power combiner in the primarypath, the second harmonic-wave attenuation circuit being configured toattenuate a signal in a frequency range of the second-harmonic wave. 7.The power amplifier circuit according to claim 5, wherein thesecond-harmonic-wave attenuation circuit comprises a fourth amplifierconfigured to amplify the input signal outputted to the primary path bythe power divider.
 8. The power amplifier circuit according to claim 1,wherein the filter circuit is arranged outside a semiconductor chip atwhich the first amplifier is arranged.
 9. A power amplifier circuitcomprising: a power divider configured to divide an input signal, and tooutput the divided input signal to a primary path and a secondary path;a distortion compensation circuit in the secondary path; a powercombiner configured to combine a fundamental wave of the input signalfrom the primary path with a second-harmonic wave of the input signalfrom the secondary path; and a first amplifier configured to amplify acombined signal outputted from the power combiner, and to output anamplified signal; a third amplifier in a stage preceding the powerdivider, the third amplifier being configured to output the inputsignal; and a second-harmonic-wave attenuation circuit between the powerdivider and the power combiner in the primary path, the secondharmonic-wave attenuation circuit being configured to attenuate a signalin a frequency range of the second-harmonic wave, wherein the distortioncompensation circuit comprises: a generation circuit configured togenerate the second-harmonic wave of the input signal, a filter circuitconfigured to attenuate the fundamental wave and to pass thesecond-harmonic wave, and a phase adjustment circuit configured toadjust a phase of the second-harmonic wave.
 10. The power amplifiercircuit according to claim 9, wherein the phase adjustment circuit isconfigured to change the phase of the second-harmonic wave such that asignal obtained as a difference between the second-harmonic wave and thefundamental wave is substantially antiphase with, at an output of thefirst amplifier, a third-order intermodulation distortion occurring inthe first amplifier.
 11. The power amplifier circuit according to claim9, wherein the second-harmonic-wave attenuation circuit comprises afourth amplifier configured to amplify the input signal outputted to theprimary path by the power divider.